Mechanical Seal Selection
Mechanical Seal Selection
(OP)
I need to select the material for an oring that will provide the best seal with minimum leakage for helium gas at 500 psi. What do you recommend? Buna-N? Vittol? Other?
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Mechanical Seal Selection
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RE: Mechanical Seal Selection
RE: Mechanical Seal Selection
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Also read the section on explosive decompression. With helium, it's almost a guarantee that you will have a problem. Control your rates of pressure release to address this problem.
Engineering is not the science behind building. It is the science behind not building.
RE: Mechanical Seal Selection
RE: Mechanical Seal Selection
According to Parker Orings Handbook, polyurethane offers the lowest diffusivity. I've summarized it in the chart below for your convenience (all entries at room temp and tested by Parker).
What is meant by Viton with PTF wrapped???
Do any of you have experience with polyurethane orings???
Polyurethane (P0642-70) 3.6 x 10^-8
Butyl (B0612-70) 6.5 x 10^-8
Neoprene (C0557-70) 6.5 x 10^-8
Nitrile (Buna-N) (N0674-70) 8.0 x 10^-8
Fluorocarbon (Vitol)(V0747-75) 12.7 x 10^-8
Thoughts?
RE: Mechanical Seal Selection
Description
AF69/90 is a highly-developed synthetic rubber based on Aflas® FEPM polymer from Asahi Glass. James Walker compounds this grade for good RGD resistance with wide chemical compatibility.
Special features
Good rapid gas decompression (RGD) resistance.
Resistance to oils, lubricants and some fuels approaching that of fluoroelastomer dipolymers.
Excellent resistance to steam, amines, bases and hydrogen sulphide.
Aflas® compounds exhibit the best radiation resistance of all elastomers.
Temperature capability
From +5°C (at atmospheric pressure) to +205°C (+41°F to +401°F).
Typical physical properties for AF69/90
Hardness: 88 IRHD
Tensile strength: 23MPa (3336psi)
Modulus @ 50% elongation: 11MPa (1595psi)
Modulus @ 100% elongation: 21.4MPa (3104psi)
Elongation at break: 115%
Low temperature torsion modulus T70: +5°C (+41°F)
Compression set: 24 hours @ 175°C (347°F): 17%
Compression set: 24 hours @ 200°C (392°F): 19%
RE: Mechanical Seal Selection
http://www.burgmann.com/?infopoolWerkstofftabelle
And you can get Design Manual from Burgmann at
http://static.scribd.com/docs/1we1icvpfc1rf.swf
On page 14th you can find all the info about the helium
Maybe It can help you.
RE: Mechanical Seal Selection
http://www.zeonchemicals.com/hydrin
Ed Danzer
www.danzcoinc.com
www.dehyds.com